A typical process for cleaning a silicon surface will utilize successive steps of exposing the surface to liquid HF, rinsing in deionized water and then exposing the surface to a cleaning solution. Silicon substrates that are subjected to such a process typically exhibit a finite amount of carbon contamination.
One known prior art technique for reducing the amount of carbon contamination is, in the initial step mentioned above, to utilize HF vapor instead of HF liquid. Although this lessens the carbon contamination, it does not eliminate it.
The prior art contains suggestions that the carbon contamination may be introduced during the rinse with deionized water. Assuming this is the case of the carbon contamination, the most obvious solution is to eliminate, or at least considerably reduce, the carbon content of the deionized water. However, this would be quite difficult because the very small carbon fragments produced by ion exchange resin columns used in producing deionized water cannot be easily filtered.
Another obvious method of eliminating the carbon from the water would be to produce the water by distillation. However, this is undesirable because distillation consumes a great deal of energy and is quite costly.
In the IBM Technical Disclosure Bulletin, October 1977, pages 1746-1747, K. D. Beyer, one of the inventors of this new cleaning process, suggested that silicon surface cleaning can be achieved by exposing silicon surfaces to HF/H.sub.2 O vapor, and then immediately immersing the substrate into a water-based cleaning agent. As part of our invention, we have verified the general correctness of that suggestion, we have discovered the manner in which the cleaning process is dependent upon the doping of the silicon surface and we have discovered various operational parameters related to the process.